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Abstract

Predictability characteristics of the wintertime stratospheric polar vortex are examined through the systematic error and the ensemble spread of the predicted north polar temperature by the operational 1-month ensemble forecast of the Japan Meteorological Agency during 7 winters. It is revealed that in early winter, the systematic error has significantly large positive values due to the underestimation of the equatorward propagation of planetary waves in the stratosphere. The estimated predictable period based on the ensemble spread according to Lorenz (1982) attains a maximum in early winter (more than 30 days) and gradually decreases with the seasonal march.